A heart can be considered the center of a circulatory system within a body. For example, the heart can take deoxygenated blood from elsewhere in the body and provide it to the lungs to be oxygenated. The heart can then supply the oxygenated blood from the lungs to other parts of the body. In a healthy heart, each chamber can contract in a coordinated fashion, such as to provide adequate circulation of oxygenated blood and nutrients to sustain the body.
The heart can be affected by a variety of physical and electrical abnormalities. Physical abnormalities can include, among other things, enlarging of the heart, sometimes associated with ischemia. Electrical abnormalities can include, among other things, various arrhythmias, such as due to prior infarcts, congenital defects, aging, or one or more other factors. These various abnormalities can be associated with one or more underlying acute or chronic diseases. For example, congestive or chronic heart failure can result in both physical and electrical abnormalities, such as those described above. In certain cases, a patient suffering from heart failure can experience life-threatening arrhythmias, such as a ventricular tachyarrhythmia, either caused by the heart failure condition itself or due to one or more other causes.